I just bought that book, "Obento love". It's a good book for the people don't want to make those ceative cute bento but want to learn to make basic ones. Most materials are easy to find at local supermarket.
I never heard of a bento box being so popular in america infact I never heard of a bento box until today and Im from amarica but any way I think the bento box luches are great :)
Sandwiches and bananas do get boring, trust me, I took that type of lunch with me for a long time. Now I put together leftovers and some freshly cut vegetables in a bento box and make some attempt to make it look presentable and it seems like a fresh new meal.
Americans like bento boxes because is kind of "guide" of how to combine healthy food, American woman don't know how to cook, so bento boxes are a attractive idea of how to combine healthy food like veggies with other kind of food